Venous thromboembolism (VTE) remains a frequent, but preventable complication for hospitalized patients that can lead to significant morbidity and mortality. It has been estimated that more than 900,000 VTE cases occur in the US every year. A range of VTE prevention interventions have been evaluated, such as electronic reminders and clinical decision support (CDS) for VTE risk assessment. Health information (IT) may provide an opportunity for improving the prevention and management of VTE. However, studies of electronic alerts based on computerized VTE risk assessment have produced limited benefits. These studies have been restricted to high-risk patients, have focused on prophylaxis (i.e. VTE prevention) with little or no consideration for VTE diagnosis and treatment (i.e. VTE management), and have not addressed sociotechnical challenges related to CDS design identified in numerous reports. We propose to use a sociotechnical systems approach to the design of health IT specifically for preventing and managing VTE; this approach can address the range of sociotechnical system issues that have limited the effectiveness of health IT for VTE. Using the SEIPS model and the human factors multi-level system model, we will develop a deep understanding of the cognitive and team work involved in VTE prevention and management, and then use the outputs of this analysis to define sociotechnical design requirements for a CDS that supports cognitive and team work for preventing and managing VTE. Our specific aims are: (1) to evaluate the cognitive and team work involved in VTE prevention and management; and (2) to develop design requirements for a CDS that supports cognitive and team work for preventing and managing VTE. The study will be conducted in four hospitals of an integrated healthcare system. Methods for analyzing cognitive and team work will be diverse (i.e. observation, interview, focus group and survey) (Aim 1) and will produce a range of outputs (e.g., decision ladders, process map, information flow diagram) that will be used to define the CDS design requirements (Aim 2). Using a collaborative process between the human factors engineers and the physicians on the research team, we will develop preliminary design requirements that will be embedded in CDS mock-ups; the CDS mock-ups will then be evaluated through scenario-based usability evaluation and group debriefings. The results of this analysis will help to define additional questions to address in the data collection for Aim 1. When all Aim 1 data have been collected and analyzed, we will finalize the CDS design requirements (Aim 2). This research focuses on VTE, but the broader objective is to develop an approach to design health IT applications for healthcare quality and safety problems that can benefit from improved integration of guidelines in clinical workflows. This study is significant and innovative because we are (a) addressing a common, but preventable complication, i.e. VTE; (b) using a sociotechnical systems approach and human factors principles and methods to design health IT; and (c) involving a highly experienced multidisciplinary team of human factors engineers and physicians.